Turning Light Into Matter: Programmable Microstructures Via Dose Control in Two‐Photon Polymerization

ABSTRACT In two‐photon polymerization (TPP), the degree of conversion (DC) of the resin affects a broad range of material properties including refractive index (RI), stiffness or shrinkage. Heterogeneous DC can substitute multimaterial or doped structures, and outright enable a new paradigm of bio‐mimicking or numerically optimized structure designs. This work presents a new approach to variable‐DC fabrication: structures are described as voxelized distributions of the desired material property, such as the RI, which the slicer converts into a dose distribution map addressed via printing laser power modulation. The versatility of this method is demonstrated by the fabrication of the C. elegans worm phantom with the most complex 3D RI distribution programmed to date, as the design was derived directly from the RI tomography imaging data. Optimized calibration methodology for the RI reveals excellent repeatability, accuracy ( 0.1%), uncertainty ( 0.001), and stability (1 year) of the RI across achievable DC. The presented workflow also enables grayscale lithography for reduced surface roughness and efficient precompensation strategies. In summary, this work provides an open source toolbox for augmenting TPP systems with a new degree of freedom and facilitates the widespread adoption of TPP fabrication with point‐wise dose control.